Comparing the reactivity of different natural clays under thermal and alkali activation

RILEM Technical Letters

article

Ahmed Zohair Khalifa¹  Yiannis Pontikes²  Jan Elsen³  Özlem Cizer¹ 

[1] Department of Civil Engineering;Department of Materials Engineering, Department of Earth and Environmental Sciences;KU Leuven, Department of Earth and Environmental Sciences

关键词: Geopolymer;    Common clays;    Alkali activation;    Thermal activation;   

DOI  :  10.21809/rilemtechlett.2019.85

学科分类：社会科学、人文和艺术（综合）

来源: RILEM Publications SARL

【 摘 要 】

Metakaolin is one of the most popular solid aluminosilicate precursors for the synthesis of geopolymers. Despite its high reactivity and availability, there is a noticeable move towards the use of other natural clays as alternative precursors, due to their plentiful supply and widespread availability. Natural clays usually consist of a combination of 1:1 and 2:1 layer silicates reactivity of which vary. In this work, four different natural clays (SS, BS, MS and WS) composed of 1:1 and 2:1 clay minerals at different proportions were studied for the synthesis of geopolymers. To increase their reactivity prior to alkali activation, the clays were calcined in a laboratory oven at different temperatures (700, 750, 800, 850, 900 °C) and different holding times (10 seconds to 60 minutes). The reactivity of the calcined clays was assessed by the dissolution test and isothermal conduction calorimetry. NaOH and a mix of NaOH and Na2SiO3 were used as alkaline activators. The results show that the optimum calcination temperature of SS, BS and MS is 800 °C with a holding time of 10 minutes. WS is sufficiently calcined at a higher temperature of 900 °C for 20 minutes. Kaolinite-rich clays (SS) present more reactivity towards alkali activation than clays dominated by smectite or illite.

【 授权许可】

CC BY